Fumaric acid is an important basic organic chemical raw material and bulk chemical product widely used in the areas of coating material, resin, pharmaceutical material, plasticizer and food additive, etc, having important commercial values. Fumaric acid can also be used as raw material for further synthesizing a number of high-value derivatives, such as DMF and ferrous fumarate. Furthermore, as an important four-carbon platform compound, fumaric acid may be used as a base material for the synthesis of various four-carbon compounds, such as L-aspartic acid, malic acid, succinic acid, maleic acid, 1,4-butanediol, Y-butyrolactone and tetrahydrofuran, via enzyme catalytic conversion, esterification and hydrogenation.
At present, commercial fumaric acid is mostly produced by chemical methods, such as the catalytic oxidation of benzene or butane to produce maleic acid or maleic anhydride, and then to obtain fumaric acid by isomerization. However, it is now facing the main difficulties due to the shortage of fossil resources, increase in production cost and pollution to the environment. The oil crisis in the 1970s forced people to make more efforts in the research of producing fumaric acid through microbial fermentation, and mycete, yeast and bacteria have been used for fermentation. Among them, Rhizopus became the focus of research for its features of simple culture requirements, high adaptation to environments and fast growing, and the family includes rhizopus oryzae, rhizopus arrhizus and rhizopus nigricans. Rhizopus oryzae, as one of the best strains for producing fumaric acid, has attracted an extensive attention.
However, commercial production of fumaric acid with fermentation methods has not been realized because of high raw material cost, which accounts for the most in the total production cost, and cutting the raw material cost has become the key for microbiol production of fumaric acid (Gangl I C, Weigang W A, Keller F A. Appl Microbiol Biotechnol, 1990, 24-25(1): 663-667), but the fumaric acid yield is quite low by using traditional processes with cheap starch as raw material (Moresi M, Parente E, Petruccioli M, Federici F J. Chem Tech Biotechnol, 1992, 54(3): 283-290; Carta F S, Soccol C R, Ramos 25 LP, Fontana J D. Bioresour Technol, 1999, 68(1): 23-28). Therefore, improving strains by widening the substrate spectrum has become the primary task. Researches show that, 2-Deoxyglucose (2-DG) is a glucose analog that can cause severe catabolite repression when strains synthesize hydrolase (glucoamylase, cellulase, xylanase and glucosidase), therefore it is often used to screen for mutants with high glucoamylase activity resisting to catabolite repression (Ghosh A, Chatterjee B, Das A Biotechnol Lett, 1991, 13(7): 515-520; Sarangbin S, Kirimura K, Usami S, Appl Microbiol Biotechnol, 1993(2-3), 40: 206-210; Chandra M, Kalra A, Sangwan N S, Gaurav S S, Darokar P M, Sangwan S R. Bioresour Technol, 2009, 100(4): 1659-1662). If the glucoamylase activity of Rhizopus oryzae can be increased, fumaric acid can be produced by simultaneously saccharifying starchy material and fermenting it without the need to saccharify the raw material first.